It isn't an assumption. It is a lack of evidence. If you have evidence, bring it forth. I mean something other than your own faith, an ancient book, and a bunch of people who believe what you do. I mean actual evidence. Make an amputee's arm grow back or spell your name in stars or something. Split the moon in half and put it back together. These things apparently could happen back before we could record them on video... not so much now. I wonder why that is....
First, atheism is not a belief system. It is the lack of a belief in Gods. That's all.
Second, I don't invest much of my life into it. I do take an interest in the phenomenon of religious belief and I do that from a sociological and psychological perspective. Wouldn't you if you were surrounded by people who believe in imaginary beings running everything and dedicate their entire lives to serve them? I think you'd be pretty fascinated by that too if you were not one of them.
It is the only rational choice and it isn't really a choice at all. I see no evidence in a fantastic claim like Gods or Ghosts or Big Foot, so I don't believe they are real.
Unlike jabeady, I DO see you as delusional, and I have no qualms in saying so. You believe in an imaginary person and dedicate your life to him. If that isn't delusion, what is? I also don't take offence if you consider me spiritually blind or delusional myself to not see what you say is obvious.